More than 2000 workers on the $52 billion Gorgon gas project staged a protest at the weekend over bunk bed arrangements for workers.
The workers were on a day off when they walked through the Barrow Island camp to show anger at fly-in, fly-out workers who accepted an offer to earn an extra $125 a day for sharing a room.
Last week The West Australian reported that the workers had turned on their colleagues calling them "scabs" on social media for accepting the offer.
The bunk bed arrangement has been offered for years but the backlash started only weeks ago when those opting to share a room started copping abuse from angry unionists.
Workers are given the extra money to share a bunk bed with someone on an opposite shift, with one assigned the room to sleep while the other is at work.
CFMEU assistant secretary Joe McDonald said the unionists were angry that workers were accepting an extra $800 a week to share rooms because there were fears that all workers would eventually be made to share without compensation.
"I remember the struggle to get individual accommodation, and now some workers are giving it away," Mr McDonald said.
AMWU secretary Steve McCartney said FIFO workers started losing hard-won conditions in 2010 when "motelling" was introduced at Woodside's Pluto site, forcing workers to change dongas at the start of every swing.
"Motelling started this slippery slope and we don't know where it will end," he said. "Multinationals will stop at nothing in their pursuit of extra profits."
Mr McCartney would not rule out industrial action if the practice was forced on workers.
A spokesman for major Gorgon joint venture partner Chevron said the arrangement was necessary because of a shortage of beds during its peak construction period."A proportion of rooms at the project's camp are being converted to dual occupancy, with these rooms being occupied by two people on opposite shifts," he said.